320A service

[zekeymonkey]

I'm currently working on planning the electrical service for my garage that will hopefully start construction by the end of May. I've decided to go with a 320A service since I can. The cost difference should be small.

As I understand it, I can use two load centers connected to the meter socket. Is it true that each of the load centers can have 200 A breakers? Or should they have main breakers that add up to 320 or less?

 

[dw1]

Yes, residential, you can have 2-200 amp breakers on your 320/400 amp service, talk to your power company on which equipment to use, here is a Milbank, just to show you whats available.
http://www.milbankworks.com/catalogs/320MBC4031_5059.pdf

 

[James-W]

I never heard of a 320 amp service. I thought a residential electrical service was either 100 amp, 200 amp, or 400 amp.

 

[Stuff]

Something about continuous load. 80% of 400 is 320.

 

[Dick in Wisconsin]

I never heard of a 320 amp service. I thought a residential electrical service was either 100 amp, 200 amp, or 400 amp.

I thought the same thing, but I was offered 320 for a cost of $3,800 on a service upgrade.

I said that was TOO much money.

Now we're taking 240amps. Waiting for the proposed cost.

My current 200amp service cuts across the corner of the new shop by about 10". Getting a new service in has been a huge fiasco!

 

[alfredeneuman]

Now we're taking 240amps. Waiting for the proposed cost.

I don't think there's such a thing as a 240 Amp Service ..... You might be waiting for a long time.

 

[wyliesdiesels]

I never heard of a 320 amp service. I thought a residential electrical service was either 100 amp, 200 amp, or 400 amp.

A 400a residential service is 320a continous...past that u need CT metering...

I don't think there's such a thing as a 240 Amp Service ..... You might be waiting for a long time.

 

[DC73]

The 320 A generally refers to the meter base. I went this route as well. I couldn't get power to the new workshop from the house without upgrading the underground service to the house and digging from the house to the new shop was going to be a major undertaking. I could easily get power from the alley for the new shop but I didn't want to have a separate meter due to the additional monthly meter charge. The local Coop (power company) recommended a 320 A meter base as those bases have lugs for two services. The additional expense to set this up will pay for itself in less than one year due to avoiding the 2nd monthly meter charge.

DC

 

[sberry]

Only down side is its a pain to disconnect for temp power.

 

[gutted72]

Do they make a 320 panel with out a meter head on it?

My electric company is supplying the meter head and it has it's own box and I provide the rest.

 

[2gslse]

I went with the upgraded service in my home when I built it ,knowing I will build a real garage in the future and its nice having 2 separate panels side by side that are not cluttered (2) 42 circuit cutler hammer panels with a total of 43 circuits between them each one has its own main breaker and can be killed to work in a dead panel and not be in the dark or future genset for essential loads if planned correctly(water pump,fridge,furnace and lighting critical areas) when main power is restored the rest of the house will light up.

 

[James-W]

A 400a residential service is 320a continuous...past that u need CT metering...

I wasn't aware of that. I had thought a 400 amp service was just that, a 400 amp service. Thank you. I learned something again today.

 

[checkthisout]

I upgraded to 320 as well. It was free for reasons too long to explain.

I'll tell you this. You don't need it unless your house and a biiiiigggg shop will be using electric heat and you plan on keeping both real warm.

400 amp service = 96,000 WATTS.

You gonna be growing something?

 

[zekeymonkey]

I don't know why they call it 320A instead of 400 A. As I understand it, a 200A service is only rated for 160A continuous.

At this point I don't need the 320A service, but the only real cost difference will be the meter base and an extra 200A panel. It looks like the cost difference for me will be around $500 between 200A and 320A. I figure it's worth it just in case I find some crazy reason to need it.

The utility will be setting a 25kVa pad mount transformer about 60 ft from the garage. I will need to dig a 40" deep trench 300 ft to the pole for the primary. Then I will need to dig a 60 ft trench to the garage for the secondary. Luckily, they will pull the wire in these underground conduit.

 

[checkthisout]

I don't know why they call it 320A instead of 400 A. As I understand it, a 200A service is only rated for 160A continuous. .

As others have stated, it's 80% continuous of 400 AMPS. I think they do that to designate between home and commercial service which generally uses inductive metering.

Ponder that for a second.....320 amps continuous is 70,400 watts or about 100 horsepower.

At this point I don't need the 320A service, but the only real cost difference will be the meter base and an extra 200A panel. It looks like the cost difference for me will be around $500 between 200A and 320A. I figure it's worth it just in case I find some crazy reason to need it..

You'll never need it. I can't think of anything other than a ton of electric heaters that would chew up that much amperage. A house with gas heat and hot water generally has 100 amp service. If heat and hot water are electric then service is 200 amps with a lot of room to spare even at that.

But ya know...if it's cheap, why not? It's always easy to get carried on stuff like that.

All GJ posters have the same affliction......

The utility will be setting a 25kVa pad mount transformer about 60 ft from the garage. I will need to dig a 40" deep trench 300 ft to the pole for the primary. Then I will need to dig a 60 ft trench to the garage for the secondary. Luckily, they will pull the wire in these underground conduit.

Yeah, you probably need to get the trenches inspected after you lay the conduit before it's buried but I'm sure you know the deal already.

The utility provided the conduit for mine from the transformer on the street to the 3" stub out in the trench just below the meter panel.

From the street I have 6 wires total. I can't quote cable sizes but whatever size wire they use for 200 AMP service, they used six of them total...so 2 wires for each phase and the neutral.

 

[sberry]

Instant water heaters are hogs. Agreed, you wont see that kind of load. I got a lot of stuff and figure my peak to be in the 100A or so range if welding when air comes on, coolers running, watering lawns and a cloths dryer could put it over the edge.

 

[zekeymonkey]

But ya know...if it's cheap, why not? It's always easy to get carried on stuff like that.

All GJ posters have the same affliction......

Too true.

Yeah, you probably need to get the trenches inspected after you lay the conduit before it's buried but I'm sure you know the deal already.

Luckily all I need is for the guy from the electric company to come out and confirm the depth. To quote the guy, "I usually like to come out and look at the trench while it's open."

 

[barnjunkie]

I went with the upgraded service in my home when I built it ,knowing I will build a real garage in the future and its nice having 2 separate panels side by side that are not cluttered (2) 42 circuit cutler hammer panels with a total of 43 circuits between them each one has its own main breaker and can be killed to work in a dead panel and not be in the dark or future genset for essential loads if planned correctly(water pump,fridge,furnace and lighting critical areas) when main power is restored the rest of the house will light up.

That's what I did and like that arrangement. If you split the panel wiring, you can have one on a generator to power the essential stuff as well. Plus I had room for surge protectors as well. This is a 320/400 service.....

 

[MagKarl]

I have a 320A service with two CH panels just like barnjunkie. I put all the essentials on one side with an interlock cover and generator back feed breaker. It works really well in my opinion.

 

[ard]

I put in a 400A service when we built the place for flexibility. Two 200A disconnects, one feeds a 200A sub for the entire house. The other 200A feeds a panel in the main that has garage service, then 100A to barn, then all my outdoor circuits. Plus my solar tie is on that panel in the main box. I never draw 400, or even 320, or even close.

Funny story, Christmas eve I am working in the shop down in the barn and every time I use the big table saw the house lights dim. Different 200A disconnect. Cannot be anything on my side of the $$$ line that is causing this voltage drop. Throw a meter on the legs and when I draw 30A on one phase the other seems to drop to 70V

Call the utility, get this gal that first tells me repeatedly "call an electrician"...then when I explain 'I have a 400Amp service with ...' she interrupts and tells me "there is no such thing!"

"could I speak to a supervisor?"

So...guys come out, one of the taps on the transformer on the pole took a dump. So he has to call out another crew- now they have two trucks out there on christmas eve day to mount a new transformer.

So I apologized to them about dragging them out in the brutal california winter on eve. Guy laughed, said "No, thank YOU- you have any idea what they pay after 5PM today?! I'm getting triple time for another 8 hour shift if this goes past 5PM". And it did, by 15 minutes.

 

[toplessHO]

trying hard to figure out why you need a 400A service
everything isnt run at once.
Have you done a load calc?

 

[sberry]

As he mentioned he really didn't but sometimes it doesn't cost much more. I did one of my own where that was the case, needed another panel anyway and a few ft of wire I already had.

 

[barnjunkie]

My reason was to provide space for an all electric home. Two water heaters, two air conditioners, double oven, detached shop, generator, plus room for future unknowns like vehicle charging, solar, etc .
It is true that all loads would not likely be needed at once, but when you have all electric appliances, its better to have too many available breaker spaces and available amps than not enough.

 

[zekeymonkey]

If it wasn't just the cost of the meter base and extra panel I wouldn't do it. But, I'm likely going to need a sub panel in the future for more space. So, it's really just the cost of the meter base. So, why not? The big cost for the install will be there if I have 100A or 500A service.

 

[Autorotica]

I upgraded from a 200A meter base to a 320/400 so I could employ a 2nd set of lugs to power the shed thru a single meter on my property. House already had a 200A panel and now the shed has its own 200A panel too.

Its all about options.
Chris